This invention relates generally to devices using electromagnetic radiation x-rays and/or gamma rays (EMRXG) and methods for using the same. More particularly, this invention relates to an exempt EMRXG source that can be used in an x-ray fluorescence device, including a portable x-ray fluorescence device, and a method for using the same.
There has been significant interest in apparatus and methods for identifying and verifying various materials or products such as explosives, ammunition, paint, petroleum products, and documents. Known methods used to identify and verify generally involve adding and detecting materials like code-bearing microparticles, bulk chemical substances, and radioactive substances or using the material element constituents. Other methods used for identifying and verifying materials include those described in U.S. Pat. Nos. 6,501,825, 6,477,227, 6,200,239, 6,030,657, 6,024,200, 6,007,744, 6,005,915, 5,849,590, 5,760,394, 5,677,187, 6,670,239, 5,474,937, 5,301,044, 5,208,630, 5,057,268, 4,862,143, 4,390,452, 4,363,965, and 4,045,676, as well as European Patent Application Nos. 0911626, 0911627, and 02723211.5.
It is also known to apply materials to articles in order to track, for example, point of origin, authenticity, and their distribution. In one method, inks that are transparent in visible light are sometimes applied to materials and the presence (or absence) of the ink is revealed by ultraviolet or infrared fluorescence. Other methods include implanting microscopic additives that can be detected optically. However, detecting these materials is primarily based on optical or photometric measurements.
Numerous devices are known for identifying and verifying articles containing such materials (called taggants) by x-ray fluorescence (XRF). See, for example, U.S. Pat. Nos. 5,461,654, 6,130,931, 6,041,095, 6,075,839, 6,097,785, and 6,111,929. Unfortunately, many of the known apparatus are unsatisfactory for several reasons. First, they are often difficult and time-consuming to use. In many instances, a sample of the article must be sent to an off-site laboratory for analysis. In other instances, the apparatus are often expensive, large, and difficult to operate. For example, the known apparatus and methods for identification and verification are also unsatisfactory because the devices employed are usually not portable.
Second, the known devices are unsatisfactory because of the governmental licensing requirements needed for the EMRXG sources used in XRF devices. The EMRXG sources are radioactive and are regulated by numerous governmental entities because of the amount of radioactivity. While x-ray tubes, which are not radioactive, can be used as an x-ray source in XRF devices, they are often not used because XRF devices containing them are still quite large and are very expensive.